Heavy duty pneumatic radial tires with organic fiber cord bead reinforcing layer

ABSTRACT

A tire wherein one or more rubberized organic fiber cord layers extending over an end of a carcass turnup portion in a radial direction of the tire are arranged so as to extend from a position near to an outside of the bead core over the end of the turnup portion toward the outside of the tire and spread apart to the turnup portion. A tire wherein one or more rubberized organic fiber cord layers are arranged so as to extend from a position exceeding over an end of a bead portion reinforcing layer made of a steel cord layer toward the outside of the tire extending over the end of the turnup portion in the radial direction of the tire and spread apart to the reinforcing layer. And also, a tire wherein a cord layer portion of one or more rubberized organic fiber cord layers extending over the end of the turnup portion in the radial direction of the tire and outside the turnup portion has a first bent portion bending toward the inside of the tire.

TECHNICAL FIELD

[0001] This invention relates to a heavy duty pneumatic radial tire, andmore particularly to tires suitable for use in vehicles such as truck,bus and the like, and particularly it relates to a heavy duty pneumaticradial tire in which an organic fiber cord layer is used in a beadportion of the tire used under severer conditions of load, running speedand the like as a reinforcing layer effective for the bead portion toimprove a bead portion durability.

BACKGROUND ART

[0002] In the heavy duty pneumatic radial tire suitable for use intrucks, buses and the like, it is common to reuse as a base tire forrecapping when a tread rubber reaches a service limit in the wearingbecause it is not desirable to use a new tire only once. Referring toFIG. 16 illustrating a section of a main part of the conventional tireinclusive of a bead portion, there is often observed a case of causing along and large crack or a separation failure accompanied with the growthof the crack in an end 4 te of a turnup portion 4 t of a carcass 4 or anouter end 6 e of a rubberized steel cord layer (generally called as awire chafer) 6 as a reinforcing layer for a bead portion 1 among membersconstituting the bead portion 1. The used tire having such defects isunsuitable as a base tire and it is obliged to give up recappingthereof. When the service conditions are very severe, the aforementionedcrack or separation failure is caused even in the new tire on the way ofthe service life.

[0003] The aforementioned long crack or separation failure in an endportion such as end 4 te, end 6 e or the like results from theconcentration of large strain in such end portion. Referring to FIG. 17showing a section of another conventional tire, in order to eliminatethis strain, there is widely used means that one or more organic fibercord layers, two layers in the illustrated embodiment, for example,nylon cord layer 15 (15-1, 15-2) generally called as a nylon chafer arearranged outside the turnup portion 4 t of the carcass 4 alone in caseof FIG. 16 or together with the steel cord layer 6 as the reinforcinglayer in case of FIG. 18 and adjacent thereto at a height sufficientlycovering the above end portion in a radial direction of the tire.

[0004] However, the application or addition of the organic fiber cordlayer 15 does not develop an effect to an intended extent and reasonsthereof are investigated to elucidate the following facts.

[0005] That is, as a part of the two organic fiber cord layers 15-1,15-2 (see FIG. 17, FIG. 18) is perspectively shown in FIG. 19 showing ahalf lower-side of a tire running under loading at a zone ranging from aleading edge of a contact patch to a trailing edge thereof, cords C_(R)(upward to the right in the figure) and cords C_(L) (upward to the leftin the figure) of the organic fiber cord layers 15-1, 15-2 are arrangedso as to cross with each other between the layers in a bead portion 1corresponding to a ground contact region of the tire tread rotatingunder a given air pressure and under loading, so that even in eithercase of arrangements upward to the left and the right, the cords have tobe always subjected to compression deformation at the leading side orthe trailing edge of the contact patch.

[0006] Although detail reason of always causing the compressiondeformation will be described later, the degree of compressiondeformation becomes more higher when the traction force and brakingforce are further applied to the tire. When axial compression force isapplied to the cord in the organic fiber cord layer 15, modulus of theorganic fiber cord becomes very low to the axial compression, so thatthe rigidity required for developing stress mitigating function of theorganic fiber cord layer 15 naturally intended to the turnup end 4 te ofthe carcass 4 or the end 6 e of the reinforcing layer 6 is largelydiminished. According to experiments, a ratio of axial compressionmodulus to tensile modulus in the organic fiber cord layer embedded inrubber is only about 0.1.

[0007] And also, it has been confirmed that cracking failure is causedin an end portion of the organic fiber cord layer 15 toward the outsideof the tire. As a result of investigation on the cause of the crackingfailure, it is elucidated to be caused by a large tensile strain appliedto rubber in the vicinity of the end 15 e of the organic fiber cordlayer 15 toward the outside of the tire. That is, an air pressure filledin the heavy duty pneumatic radial tire mainly used in the truck and busis as high as 7.00˜9.00 kgf/cm², for example, at room temperature and isfurther increased by rising of tire temperature accompanied with therunning of the vehicle. As shown in FIG. 18, a large tension T isapplied to the carcass 4 by such a higher internal pressure, and thelarge tension T produces pulling forces a, b of arrow direction in notonly the turnup portion 4 t of the carcass 4 but also the bead portionreinforcing layer 6 and the organic fiber cord layer 15 and hence theturnup portion 4 t, bead portion reinforcing layer 6 and organic fibercord layer 15 are forcibly displaced in the acting direction of thepulling forces a, b. By such a forced displacement is particularlycaused a large tensile strain e in rubber near to the end 15 e of theorganic fiber cord layer 15. The tensile strain e is further increasedby bending deformation of the bead portion 1 under loading shown by aphantom line. Consequently, fatigue crack is created in rubber near tothe end 15 e of the organic fiber cord layer 15 by repetitive action ofstrain amplitude of the tensile strain e accompanied with the rotationunder loading, which grows to finally cause the separation failure.

[0008] In addition, it is strongly demanded to form a lower sectionprofile of radial ply tires for recent trucks and buses, from which ittends to increase low-section tires. In the low-section tire used underheavy load, the deformation of the bead portion 1 is particularlyincreased and the strain amplitude quantity of the tensile strain e isconsiderably increased, so that there is highlighted cracking failure orseparation failure in the end 15 e of the organic fiber cord layer 15located toward the outside of the tire, which has hardly been observedin the conventional tire. This type of the failure is a recent tendencyand an effective improving countermeasure is not existent up to thepresent time.

[0009] It is, therefore, an object of the invention to provide a heavyduty pneumatic radial tire in which the organic fiber cord layeradvantageously develops the rigidity as a stress mitigating layer to theend of the turnup portion of the carcass and the end of the bead portionreinforcing layer made of the steel cord layer extending over the turnupend outward in the radial direction of the tire and also the resistanceto cracking in the end of the organic fiber cord layer is largelyimproved even in a tire having a small aspect ratio to considerablyimprove the bead portion durability and recapping property as comparedwith the conventional tire.

DISCLOSURE OF THE INVENTION

[0010] In order to achieve the above object, a first aspect of theinvention lies in a heavy duty pneumatic radial tire comprising acarcass of at least one rubberized cord ply of radial arrangementtoroidally extending between a pair of bead core embedded in beadportions and wound around the bead core from inside of the tire towardoutside to form a turnup portion, and at least one rubberized organicfiber cord layer extending outside the turnup portion over an end of theturnup portion outward in a radial direction of the tire, in which theorganic fiber cord layer is arranged so as to extend from a positionnear to an outside of the bead core over the end of the turnup portiontoward the outside of the tire and spread apart to the turnup portion.

[0011] In a preferable embodiment of the first aspect of the invention,the organic fiber cord layer has a first bent portion acutely bendingtoward the outside of the tire with respect to a winding direction ofthe turnup portion extending outward from the position near to theoutside of the bead core in the radial direction, and a bending angle αof the first bent portion with respect to the winding direction of theturnup portion at a radial section of the tire is within a range of15˜60°.

[0012] In another preferable embodiment of the first aspect of theinvention, a bead portion reinforcing layer made of a rubberized steelcord layer is disposed between the turnup portion of the carcass and theorganic fiber cord layer and an outer end of the reinforcing layer inthe radial direction of the tire locates inward from the end of theturnup portion in the radial direction of the tire.

[0013] In the other preferable embodiment of the first aspect of theinvention, an end of the first bent portion of the organic fiber cordlayer is an outermost end in the radial direction of the tire.

[0014] In a still further preferable embodiment of the first aspect ofthe invention, the organic fiber cord layer has the first bent portionand a second bent portion again bending from an end of the first bentportion toward an inside of the tire, and an inclination angle β of thesecond bent portion inclined with respect to the winding direction ofthe turnup portion is within a range of 15˜60° at the radial section ofthe tire.

[0015] In a further preferable embodiment of the first aspect of theinvention, the organic fiber cord layer has the first bent portion, thesecond bent portion and a third bent portion extending outward from anend of the second bent portion at an approximately equal distance to anouter surface of the tire in the radial direction of the tire.

[0016] In another preferable embodiment of the first aspect of theinvention, the organic fiber cord layer has the first bent portion andthe third bent portion extending outward from the end of the first bentportion at an approximately equal distance to an outer surface of thetire in the radial direction of the tire.

[0017] In the other preferable embodiment of the first aspect of theinvention, the organic fiber cord layer has the first bent portion, thethird bent portion and a fourth bent portion extending from the thirdbent portion toward the inside of the tire and acutely inclining withrespect to the winding direction of the turnup portion.

[0018] The inclination angle γ of the fourth bent portion with respectto the winding direction of the turnup portion is within a range of15˜60° at the section of the tire.

[0019] In order to achieve the above object, a second aspect of theinvention lies in a heavy duty pneumatic radial tire comprising acarcass of at least one rubberized cord ply of radial arrangementtoroidally extending between a pair of bead core embedded in beadportions and wound around the bead core from inside of the tire towardoutside to form a turnup portion, at least one bead portion reinforcinglayer made of a rubberized steel cord layer extending outside the turnupportion over an end of the turnup portion, and at least one rubberizedorganic fiber cord layer extending outside the turnup portion over anend of the turnup portion outward in a radial direction of the tire, inwhich the organic fiber cord layer is arranged so as to extend from aposition near to an outside of the bead core over the end of the turnupportion of the bead portion reinforcing layer toward the outside of thetire and spread apart to the turnup portion.

[0020] In a preferable embodiment of the second aspect of the invention,the organic fiber cord layer has a first bent portion acutely bendingtoward the outside of the tire with respect to the bead portionreinforcing layer extending outward from the position near to theoutside of the bead core in the radial direction and the extendingdirection thereof, and a bending angle α of the first bent portion withrespect to the winding direction of the turnup portion at a radialsection of the tire is within a range of 15˜60°.

[0021] In another preferable embodiment of the second aspect of theinvention, an end of the first bent portion of the organic fiber cordlayer is an outermost end in the radial direction of the tire.

[0022] In the other preferable embodiment of the second aspect of theinvention, the organic fiber cord layer has the first bent portion and asecond bent portion again bending from an end of the first bent portiontoward an inside of the tire, and an inclination angle β of the secondbent portion inclined with respect to the winding direction of theturnup portion is within a range of 15˜60° at the radial section of thetire.

[0023] In a further preferable embodiment of the second aspect of theinvention, the organic fiber cord layer has the first bent portion, thesecond bent portion and a third bent portion extending outward from anend of the second bent portion at an approximately equal distance to anouter surface of the tire in the radial direction of the tire.

[0024] In another preferable embodiment of the second aspect of theinvention, the organic fiber cord layer has the first bent portion andthe third bent portion extending outward from the end of the first bentportion at an approximately equal distance to an outer surface of thetire in the radial direction of the tire.

[0025] In the other preferable embodiment of the second aspect of theinvention, the organic fiber cord layer has the first bent portion, thethird bent portion and a fourth bent portion extending from the thirdbent portion toward the inside of the tire and acutely inclining withrespect to the winding direction of the turnup portion.

[0026] The inclination angle γ of the fourth bent portion with respectto the winding direction of the turnup portion is within a range of15˜60° at the section of the tire.

[0027] In order to achieve the above object, a third aspect of theinvention lies in a heavy duty pneumatic radial tire comprising acarcass of at least one rubberized cord ply of radial arrangementtoroidally extending between a pair of bead core embedded in beadportions and wound around the bead core from inside of the tire towardoutside to form a turnup portion, and at least one rubberized organicfiber cord layer extending outside the turnup portion over an end of theturnup portion outward in a radial direction of the tire, in which atleast a cord layer portion of the organic fiber cord layer located atthe side of the turnup portion has a first bent portion bending suchthat its outer end is inclined toward an inside of the tire in a radialdirection thereof.

[0028] In a preferable embodiment of the third aspect of the invention,a bending angle θ of the first bent portion with respect to the windingdirection of the turnup portion is within a range of 15˜70° at thesection of the tire.

[0029] In another preferable embodiment of the third aspect of theinvention, a bead portion reinforcing layer made of a rubberized steelcord layer is disposed between the turnup portion of the carcass and theorganic fiber cord layer, and an outer end of the reinforcing layer inthe radial direction of the tire locates inward from an end of theturnup portion in the radial direction of the tire.

[0030] In the other preferable embodiment of the third aspect of theinvention, a bead portion reinforcing layer made of a rubberized steelcord layer is disposed between the turnup portion of the carcass and theorganic fiber cord layer, and an outer end of the reinforcing layer inthe radial direction of the tire locates between an end of the turnupportion and an outer end of at least cord layer portion of the organicfiber cord layer located at the side of the turnup portion of thecarcass, and the first bent portion locates outward from the outer endof the bead portion reinforcing layer in the radial direction of thetire.

[0031] In a still further preferable embodiment of the third aspect ofthe invention, the end of the first bent portion of the organic fibercord layer is an outermost end in the radial direction of the tire.

[0032] In the first, second and third aspects of the invention and theirpreferable embodiments, it is common that each length of the first bentportion, second bent portion and third bent portion o the organic fibercord layer is within a range of 4˜50 mm.

[0033] In the first, second and third aspects of the invention, theorganic fiber cord layer is suitable to be a nylon cord layer.

BEST MODE FOR CARRYING OUT THE INVENTION

[0034] Embodiments for carrying out the invention will be described indetail with reference to FIG. 1˜FIG. 15.

[0035]FIG. 1˜FIG. 6 are diagrammatically sectional views of a main partinclusive of a bead portion at a section of a tire in a plane includinga rotating axis of the heavy duty pneumatic radial tire according to thefirst aspect of the invention;

[0036]FIG. 7˜FIG. 12 are diagrammatically sectional views of a main partinclusive of a bead portion at a section of a tire in a plane includinga rotating axis of the heavy duty pneumatic radial tire according to thesecond aspect of the invention;

[0037]FIG. 13˜FIG. 15 are diagrammatically sectional views of a mainpart inclusive of a bead portion at a section of a tire in a planeincluding a rotating axis of the heavy duty pneumatic radial tireaccording to the third aspect of the invention.

[0038] The heavy duty pneumatic radial tire shown in FIG. 1˜FIG. 15(hereinafter referred to as a tire) is a tubeless tire (hereinafterreferred to T/L tire) using a 15° drop center rim (15° DROP CENTER RIMor 15° DROP-CENTER RIM) defined in JATMA standard (1998 print) and ETRTOstandard (1998 print) as an approved rim (term defined in JATMAstandard, APPROVED RIM CONTOURS according to TRA standard, RECOMMENDEDRIMS, PERMITTED RIMS according to ETRTO standard).

[0039] In FIG. 1˜FIG. 15, the tire comprises a pair of bead portions 1(shown only by one side), a sidewall portion 2 (shown only by one side)connecting thereto and a tread portion not shown according to custom,and is provided with a carcass 4 toroidally extending between a pair ofbead cores 3 embedded in the bead portions 1. The carcass 4 is one ormore radial cord plies, desirably rubberized steel cord plies of radialarrangement. Although the showing is omitted, the tire comprises a beltsuperimposed on an outer periphery of the carcass 4 and reinforcing thetread portion, desirably two or more rubberized steel cord cross layers.

[0040] At least one ply of the carcass 4 has a turnup portion 4 t woundaround the bead core 3 from inside of the tire toward outside thereof.In the bead portion 1 is provided one or more rubberized organic fibercord layers 5, preferably rubberized nylon cord layers (so-called nylonchafer) extending at an outside of the turnup portion 4 t over an end 4te of the turnup portion outward in the radial direction of the tire(hereinafter referred to as outward in the radial direction), in whichtwo organic fiber cord layers 5-1, 5-2 are shown in FIG. 1˜FIG. 7, FIG.8˜FIG. 13 and FIG. 15 and one organic fiber cord layer 5 is shown inFIG. 8 and FIG. 15, respectively. Preferably, at least one layer of theorganic fiber cord layers 5 (5-1, 5-2) is disposed up to the inside ofthe carcass 4 in the tire.

[0041] The tires according to the first aspect of the invention areexplained in accordance with FIG. 1˜FIG. 6. The bead portion 1 shown inFIG. 1˜FIG. 4 has a structure having the organic fiber cord layers 5arranged along the turnup portion 4 t of the carcass 4, and the beadportion 1 shown in FIG. 5, FIG. 6 has a structure that the bead portionreinforcing layer 6 made of the rubberized steel cord layer 6 (shown bydotted lines) is arranged adjacent to the turnup portion 4 t and an end6 e of the reinforcing layer 6 locates inward from an end 4 te of theturnup portion 4 t in the radial direction of the tire (hereinafterreferred to as inward in the radial direction) and the organic fibercord layers 5 are arranged outside the turnup portion 4 t so as tosandwich the bead portion reinforcing layer 6 therebetween.

[0042] In the bead portion 1 shown in FIG. 1˜FIG. 4, the organic fibercord layers 5 are arranged directly adjacent to the outer surface of theturnup portion 4 t inward from the position near to the outside of thebead core 3 in the bead portion 1 or inward from a position separatedapart within a range of 2˜20 mm inward from the end 4 te of the turnupportion 4 in the actual T/L tire of the illustrated embodiments in theradial direction. In the bead portion 1 shown in FIG. 5 and FIG. 6, theorganic fiber cord layers 5 are arranged close to the turnup portion 4 tin a region adjacent to the bead portion reinforcing layer 6, and theorganic fiber cord layers 5 are arranged adjacent to the turnup portion4 t between the end 6 e of the bead portion reinforcing layer 6 and theend 4 te of the turnup portion 4.

[0043] As shown in FIG. 1˜FIG. 6, the organic fiber cord layers 5 (5-1,5-2) are arranged so as to extend from the position near to the outsideof the bead core 3 or from the position separated apart within a rangeof the 2˜20 mm inward from the end 4 te of the turnup portion 4 in theT/L tire in the radial direction toward the outside of the tire and in adirection exceeding outward from the end 4 te of the turnup portion 4 tin the radial direction and to spread apart to the turnup portion 4 t.When a distance between a start position of spreading the organic fibercord layer 5 to the turnup portion 4 t and the end 4 te of the turnupportion 4 is short, the organic fiber cord layers 5 are arranged spreadapart to the turnup portion 4 t and the winding direction thereof. Thewinding direction is described below.

[0044] In FIG. 1˜FIG. 6, the organic fiber cord layers 5 extending fromthe turnup portion 4 t so as to spread apart thereto have concretely afirst bent portion 5H₁ acutely bending outward from the position near tothe outside of the bead core 3 in the radial direction and toward theoutside of the tire with respect to the turnup portion 4 t and thewinding direction thereof. More concretely, the bending angle α of thefirst bent portion 5H₁ with respect to the turnup portion 4 t and thewinding direction thereof is within a range of 15˜60°, preferably 20˜40° at a section of the tire shown in each figure. The term “windingdirection of the turnup portion 4 t” used herein is defined by a tangent(hereinafter referred to as winding line) to a line (curved line orstraight line or a composite curve of curved line and straight line)passing through a center of a thickness in an end portion inclusive ofthe end 4 te of the turnup portion 4 at the section of the bead portion1 or a portion ranging inward from the end 4 te to a position separatedapart therefrom within a range of 2˜20 mm in the radial direction, whichis the same as above below. The turnup portion 4 t and the windingdirection thereof include both a case of inclining toward the outside ofthe tire outward in the radial direction and a case of extending in adirection perpendicular to a rotating axis of the tire outward in theradial direction and inclining toward the inside of the tire, which arethe same as above below. As to the organic fiber cord layer 5 having thefirst bent portion 5H₁, there are existent various examples as mentionedbelow.

[0045] The organic fiber cord layer 5 shown in FIG. 1 is an example thatthe end 5 e of the first bent portion 5H₁ is an outermost end in theradial direction of the tire.

[0046] The organic fiber cord layer 5 shown in FIG. 2 is an example thatthe first bent portion 5H₁ a second bent portion 5H₂ again bendingtoward the inside of the tire from an end at an outermost side positionof the portion 5H₁ are existent in a zone from the position near to theoutside of the bead core 1 to the end 5 e. As shown in FIG. 2, thesecond bent portion 5H₂ is arranged so as to extend obliquely withrespect to the winding direction of the turnup portion 4 and theinclination angle β thereof is within a range of 15˜60°, preferably20˜40°.

[0047] The organic fiber cord layer 5 shown in FIG. 3 is an examplehaving the first bent portion 5H₁, the second bet portion 5H₂ and athird bent portion 5H₃ extending outward from a bending end of thesecond bent portion 5H₂ in the radial direction so as to maintain anapproximately equal distance to the surface of the tire together, inwhich the third bent portion 5H₃ has an end 5 e.

[0048] The organic fiber cord layer 5 shown in FIG. 4 is an examplehaving the fist bent portion 5H₁ and the third bent portion 5H₃extending outward from the bending end of the first bent portion 5H₁ soas to maintain an approximately equal distance to the surface of thetire, in which the third bent portion 5H₃ has an end 5 e.

[0049] The organic fiber cord layer 5 in the bead portion 1 shown inFIG. 5 is an example wherein it locates outside the bead portionreinforcing layer 6 located outside the turnup portion 4 t in the tireand has the first bent portion 5H₁ and the third bent portion 5H₃together and terminates at an end 5 e of the third bent portion 5H₃.

[0050] The organic fiber cord layer 5 shown in FIG. 6 is an examplewherein it locates outside the bead portion reinforcing layer 6 locatedoutside the turnup portion 4 t in the tire and has the first bentportion 5H₁, the third bent portion 5H₃ and a fourth bent portion 5H₄extending from a bending end of the third bent portion 5H₃ toward theinside of the tire and acutely inclining with respect to the windingdirection of the turnup portion 4 t together. The inclination angle γ ofthe fourth bent portion 5H₄ with respect to the winding direction of theturnup portion 4 t is within a range of 15˜60°.

[0051] The aforementioned bending angle α of the first bent portion 5H₁,inclination angle β of the second bent portion 5H₂ and inclination angleγ of the fourth bent portion 5H₄ are defined as a cross angle between atangent (hereinafter referred to as bent portion tangent) to a line(curved line or straight line or a composite line of curved line andstraight line) passing through a center of a thickness in a central partof each bent portion other than a rounded bending position and a windingline at an intersect point P between the bent portion tangent and thewinding line of the turnup portion 4 t. Since there are existent pluralor many bent portion tangents and winding lines, respectively, anaverage value of plural or many cross angles is used. Moreover, when thetwo organic fiber cord layers 5-1, 5-2 are used, or even in case ofthree or more layers, all cord layers are put into the ranges of theabove angles α, β, γ. The angles α, β, γ are typically illustrated inone layer.

[0052] The tires according to the second aspect of the invention areexplained in accordance with FIG. 7˜FIG. 12. The bead portion 1 shown inFIG. 7˜FIG. 12 has a structure that a bead portion reinforcing layer 6(shown by dotted lines) made of a rubberized steel cord layer 6 isarranged adjacent to the outside of the turnup portion 4 t and an end 6e of the reinforcing layer 6 is located outward from the end 4 te of theturnup portion 4 t in the radial direction and organic fiber cord layers5 extending outward over the end 6 e of the bead portion reinforcinglayer 6 in the radial direction is arranged at the outside of the beadportion reinforcing layer 6 in the tire. In the bead portion 1 havingsuch a structure, the organic fiber cord layers 5 is arranged directlynear to the outside surface of the bead portion reinforcing layer 6 fromthe position separated apart within a range of 2˜20 mm inward from theend 6 e of the bead portion reinforcing layer 6 in the T/L tire in theradial direction. In this case, the end 4 te of the turnup portion 4 tis separated apart within a range of 5˜60 mm inward from the end 6 e ofthe bead portion reinforcing layer 6 in the radial direction.

[0053] As shown in FIG. 7˜FIG. 12, the organic fiber cord layers 5 (5-1,5-2) are arranged so as to extend from the position near to the outsideof the bead core 3 or from the position separated apart within a rangeof the 2˜20 mm inward from the end 6 e of the bead portion reinforcinglayer 6 in the T/L tire in the radial direction toward the outside ofthe tire and in a direction exceeding outward from the end 6 e of thebead portion reinforcing layer 6 in the radial direction and to spreadapart to the bead portion reinforcing layer 6. When a distance between astart position of spreading the organic fiber cord layer 5 to the beadportion reinforcing layer 6 and the end 6 e of the reinforcing layer 6is short, the organic fiber cord layers 5 are arranged spread apart tothe bead portion reinforcing layer 6 and the extending direction of thereinforcing layer 6. The extending direction of the reinforcing layer 6is described below.

[0054] In FIG. 7˜FIG. 12, the organic fiber cord layers 5 extending fromthe bead portion reinforcing layer 6 so as to spread apart thereto haveconcretely a first bent portion 5H₁ acutely bending outward from theposition near to the outside of the bead core 3 in the radial directionand toward the outside of the tire with respect to the bead portionreinforcing layer 6 and the extending direction of the reinforcing layer6. More concretely, the bending angle α of the first bent portion 5H₁with respect to the bead portion reinforcing layer 6 and the extendingdirection of the reinforcing layer 6 is within a range of 15˜60° at asection of the tire shown in each figure. The term “extending directionof the bead portion reinforcing layer 6” used herein is defined by atangent (hereinafter referred to as directing line) to a line (curvedline or straight line or a composite curve of curved line and straightline) passing through a center of a thickness in an end portioninclusive of the end 6 e of the bead portion reinforcing layer 6 at thesection of the bead portion 1 or a portion ranging inward from the end 6e to a position separated apart therefrom within a range of 2˜20 mm inthe radial direction, which is the same as above below. As to theorganic fiber cord layer 5 having the first bent portion 5H₁, there areexistent various examples as mentioned below.

[0055] The organic fiber cord layer 5 shown in FIG. 7 is an example thatthe end 5 e of the first bent portion 5H₁ is an outermost end in theradial direction of the tire.

[0056] The organic fiber cord layer 5 shown in FIG. 8 and FIG. 9 is anexample that the first bent portion 5H₁ and a second bent portion 5H₂again bending toward the inside of the tire from an end at an outermostside position of the portion 5H₁ are existent in a zone from theposition near to the outside of the bead core 1 to the end 5 e. As shownin FIG. 8, the second bent portion 5H₂ is arranged so as to extendobliquely with respect to the extending direction of the bead portionreinforcing layer 6 and the inclination angle β thereof is within arange of 15˜60°.

[0057] The organic fiber cord layer 5 shown in FIG. 10 is an examplehaving the first bent portion 5H₁, the second bet portion 5H₂ and athird bent portion 5H₃ extending outward from a bending end of thesecond bent portion 5H₂ in the radial direction so as to maintain anapproximately equal distance to the surface of the tire together, inwhich the third bent portion 5H₃ has an end 5 e.

[0058] The organic fiber cord layer 5 shown in FIG. 11 is an examplehaving the fist bent portion 5H₁ and the third bent portion 5H₃extending outward from the bending end of the first bent portion 5H₁ soas to maintain an approximately equal distance to the surface of thetire, in which the third bent portion 5H₃ has an end 5 e.

[0059] The organic fiber cord layer 5 shown in FIG. 12 is an examplehaving the first bent portion 5H₁, the third bent portion 5H₃ and afourth bent portion 5H₄ extending from a bending end of the third bentportion 5H₃ toward the inside of the tire and acutely inclining withrespect to the extending direction of the bead portion reinforcing layer6 together. The inclination angle γ of the fourth bent portion 5H₄ withrespect to the extending direction of the bead portion reinforcing layer6 is within a range of 15˜60°.

[0060] The aforementioned bending angle α of the first bent portion 5H₁,inclination angle β of the second bent portion 5H₂ and inclination angleγ of the fourth bent portion 5H₄ are defined as a cross angle between atangent (hereinafter referred to as bent portion tangent) to a line(curved line or straight line or a composite line of curved line andstraight line) passing through a center of a thickness in a central partof each bent portion other than a rounded bending position and adirecting line at an intersect point P between the bent portion tangentand the extending line of the bead portion reinforcing layer 6. Sincethere are existent plural or many bent portion tangents and directinglines, respectively, an average value of plural or many cross angles isused. Moreover, when the two organic fiber cord layers 5-1, 5-2 areused, or even in case of three or more layers, all cord layers are putinto the ranges of the above angles α, β, γ. The angles α, β, γ aretypically illustrated in one layer.

[0061] Referring to FIG. 19 previously mentioned, when the organic fibercord layer 15 in the bead portion 1 corresponding to a ground contactregion of a tread portion in the conventional tire rotating in an arrowdirection under a load W is subjected to reaction force from roadsurface at the ground contact region, cords upward to the left C_(L) aresubjected to compression in their axial direction at a positioncorresponding to the leading edge of the contact patch to indicate awaving tendency as shown, while cords upward to the right C_(R) aresubjected to compression in their axial direction at a positioncorresponding to the trailing edge to indicate a waving tendency asshown, and both cords C_(L), C_(R) are subjected together to compressionin the vicinity of a position jest under the load W (normal line of arotating axis O of the tire shown in FIG. 19).

[0062] In FIG. 18 showing a left-side section of a main part of atire-rim assembly when such a tire is assembled onto an approved rim 10,the bead portion 1˜sidewall portion 2 under an inflation of a given airpressure are shown by a solid line, and each portion under a given loadis shown by a phantom line, in which the bead portion shown by thephantom line is at a state of indicating so-called fall-down phenomenon.Such a fall-down can be grasped as a bending deformation just like thefixation of the bead portion 1 to a flange 10F of the rim and a beadseat of the rim.

[0063] This bending deformation results in a force directing from thesidewall portion 2 toward the bead portion 1, but it is difficult toavoid the action of such a force. On the assumption that the force isinevitable, considering a large triaxial strain produced in the vicinityof the end 4 te of the turnup portion 4 t having a high rigidity or inthe vicinity of the ends of the bead portion reinforcing layers 6, 15located higher than the end 4 te, when a principal strain of renderingshear strain into zero and consisting of three-direction normal strainsε₁, ε₂, β₃ is taken as a plane problem for simplification, the principalstrain shown in FIG. 18 has an inclination angle of about 45° withrespect to the end 4 te of the turnup portion 4 t or the end 6 e of thebead portion reinforcing layer 6 exceeding outward over the end 4 te inthe radial direction, and such an inclination angle is the same as theaforementioned bending angle α. The acting direction of the principalstrain is an arrow direction in FIG. 18, or a direction toward theoutside of the tire.

[0064] In the tire or T/L tire, therefore, the organic fiber cord layers5 are arranged so as to extend from the position near to the outside ofthe bead core 3 or the position separated apart within a range of 2˜20mm inward from the end 4 te of the turnup portion 4 in the radialdirection over the end 4 te of the turnup portion 4 t toward the outsideof the tire and outward in the radial direction, or from the positionseparated apart within a range of 2˜20 mm inward from the end 6 e of thebead portion reinforcing layer 6 exceeding the end 4 te of the turnupportion 4 t over the end 6 e of the bead portion reinforcing layer 6toward the outside of the tire and outward in the radial direction andspread apart to the turnup portion 4 t or the bead portion reinforcinglayer 6, or in other words, the spread organic fiber cord layers 5 isrendered into the first bent portion 5H₁, whereby the arrangingdirection of the organic fiber cords in the first bent portion 5H₁ ofthe organic fiber cord layer 5 can be matched to a tensile direction ofthe principal strain between the leading edge and the trailing edge ofthe contact patch during the rotation of the tire-rim assembly underloading to give tension to the organic fiber cords in the portion 5H₁and hence it is possible to increase the rigidity of the organic fibercord layer 5 and improve the durability of the bead portion 1.

[0065] In fact, when the bending angle α of the first bent portion 5H₁is rendered into a range of 15˜60°, preferably 20˜40°, the tension canadvantageously be applied to the organic fiber cords in the first bentportion 5H₁.

[0066] Although only the compression force has been exclusively appliedto the organic fiber cords in the vicinity of the end 4 te of the turnupportion 4 t and the outer end of the bead portion reinforcing layer 6 inthe radial direction in the conventional tire, according to theinvention, tensile force offsetting the conventional compression forcecan be applied to the organic fiber cords in the first bent portion 5H₁of the organic fiber cord layer 5, whereby the rigidity of the organicfiber cord layer 5 can be more increased as compared with theconventional one to considerably enhance the stress mitigating effect atthe end 4 te of the turnup portion 4 t and the end 6 e of the beadportion reinforcing layer 6 and finally develop the effect ofconsiderably improving the durability of the bead portion. Such effectsare effective as a value of an aspect ratio in the tire (according toJATMA standard of 1998 print, NOMINAL ASPECT RATIO in TRA of 1998 printand ETRTO of 1998 print) becomes small. In this point, the invention isfavorable to tires for truck and bus having an aspect ratio of not morethan 70.

[0067] And also, the feature that the bending length δ of the first bentportion 5H₁ and the length ε of the second bent portion 5H₂ are renderedinto a range of 4˜50 mm, respectively, is effectively contributes toimprove the rigidity of the organic fiber cord layer in the vicinity ofthe end 4 te of the turnup portion 4 t and outer end 6 e of the beadportion reinforcing layer 6 in the radial direction. The bending lengthof the third bent portion 5H₃ may be in the above range. Even in case oftwo or more organic fiber cord layers 5, each bending length of the bentportions 5H₁, 5H₂, 5H₃ is within the above range.

[0068] Finally, the tires according to the third aspect of the inventionare explained in accordance with FIG. 13˜FIG. 15. The bead portion 1shown in FIG. 13 has a structure having organic fiber cord layers 5arranged along the turnup portion 4 t of the carcass 4, while the beadportion 1 shown in FIG. 14 and FIG. 15 has a structure that a beadportion reinforcing layer 6 (shown by dotted lines) is arranged adjacentto the turnup portion 4 t and an end 6 e of the reinforcing layer 6 isterminated outward from the end 4 te of the turnup portion 4 t in theradial direction and the organic fiber cord layers 5 are arranged at theoutside of the turnup portion 4 t so as to sandwich the bead portionreinforcing layer 6 therebetween. In all bead portions 1 shown in FIG.13˜FIG. 15, the organic fiber cord layer 5 at least located at the sideof the turnup portion 4 t has a first bent portion 5H₁ bending an outerend 5 e in the radial direction toward the inside of the tire. Further,the bending angle θ of the first bent portion 5H1 with respect to thewinding direction of the turnup portion 4 t is within a range of 15˜70°,preferably 30˜60°.

[0069] As mentioned above, the first bent portion 5H₁ bending inwardtoward the inside of the tire at the outer end 5 e in the radialdirection is formed in the organic fiber cord layer 5, wherebycompression strain unavoidably produced in the bead portion 1 during therotation of the tire under loading may effectively be transmitted to thefirst bent portion 5H₁ and hence force offsetting the pulling force bapplied to the end 15 e of the organic fiber cod layer 15 in theconventional tire as previously mentioned in FIG. 18 is applied to thefirst bent portion 5H₁ to finally decrease tensile strain in the end 5 eof the first bent portion 5H₁, whereby the occurrence of cracking in theend 5 e can be controlled to improve the durability of the bead portion1. In this case, the feature that the bending angle θ of the first bentportion 5H₁ is within a range of 15˜70°, desirably 30˜60° is suitable toeffective transmission of compression to the first bent portion 5H₁.

[0070] The organic fiber cord layer 5 in the bead portion 1 shown inFIG. 13˜FIG. 15 is an example that the end 5 e of the first bent portion5H₁ is an outermost end in the radial direction of the tire. As theorganic fiber cord layer 5 having the first bent portion 5H₁, there areexistent various examples as mentioned below.

[0071] The organic fiber cord layer 5 shown in FIG. 13 is an examplethat two organic fiber cord layers 5 (5-1, 5-2) are adjacent to theoutside of the turnup portion 4 t of the carcass 4 and have a first bentportion 5H₁ bending toward the inside of the tire from a positionseparated apart in a range of 2˜30 mm outward from the end 4 te of theturnup portion 4 t in the radial direction.

[0072] The organic fiber cord layer 5 shown in FIG. 14 and FIG. 15 is anexample that a bead portion reinforcing layer 6 is adjacent to theoutside of the turnup portion 4 t and has an end 6 e exceeding outwardover the end 4 te of the turnup portion 4 t in the radial direction andthe first bent portion 5H₁ is at the outside of the reinforcing layer 6and bends toward the inside of the tire at a position separated apartwithin a range of 2˜30 mm outward from the end 6 e of the reinforcinglayer. Moreover, a case that the end 6 e of the reinforcing layer 6located inward from the end 4 te of the turnup portion 4 t in the radialdirection is included though the illustration is omitted.

[0073] And also, the feature that the length of the first bent portion5H₁ shown in FIG. 13˜FIG. 15 is within a range of 4˜50 mm is suitablefor the effective transmission of compression to the end 5 e of thefirst bent portion 5H₁.

[0074] Moreover, numeral 8 shown in FIG. 1˜FIG. 18 is a stiffener. Thestiffener 8 has a tapered hard rubber stiffener 8-1 arranged at the sideof the bead core 3 and a soft rubber stiffener 8-2 extending adjacentthereto outward in the radial direction. The inner surface of the tireis covered with an innerliner 9, which particularly uses an airimpermeable rubber in the T/L tire. It is favorable that the outer end 5e of the first bent portion 5H₁ bending toward the inside of the tire isterminated in the inside of the soft rubber stiffener 8-2.

EXAMPLES

[0075] There are provided T/L radial tires for truck and bus having asize of 11/70R22.5, in which a carcass 4 is a single rubberized steelcord ply of radial arrangement and a belt is comprised of fourrubberized steel cord cross layers. An organic fiber cord layer 5 is anylon chafer containing nylon cords of 1260D/2 at an end count of 31.0cords/5 cm, and a bead portion reinforcing layer 6 is a wire chaferhaving steel cords of 3×0.24+9×0.225+1 structure at an end count of 23.5cords/5 cm. A height of an end 4 te of a turnup portion 4 t of thecarcass 4 from a bead base line (a straight line passing through anintersect between an extension line of the bead base and an extensionline of a section of a bead portion at the side of a flange 10F of a rim10 and parallel to a rotating axis of the tire with reference to FIG.18) is 45 mm.

[0076] They are divided into a first group of Examples 1˜9 andconventional example having a structure of a bead portion 1 as shown inFIG. 1˜FIG. 6 according to the first aspect of the invention, a secondgroup of Examples 10˜17 and conventional example having a structure of abead portion 1 as shown in FIG. 7˜FIG. 12 according to the second aspectof the invention, and a third group of Examples 18˜23 and conventionalexample having a structure of a bead portion as shown in FIG. 13˜FIG. 15according to the third aspect of the invention. The bending angle α(degree) and bending angle θ (degree) of the first bent portion 5H₁,inclination angle β (degree) of the second bent portion 5H₂, inclinationangle γ (degree) of the fourth bent portion 5H₄, length δ (mm) of thefirst bent portion 5H₁ and bending length ε (mm) of the second bentportion 5H₂ are shown in Table 1 as the first group, Table 2 as thesecond group and Table 3 as the third group together with thecorresponding figure No., respectively. Moreover, the conventionalexample has a bead portion structure common to each group. TABLE 1Conventional Examples Items Example 1 2 3 4 5 6 7 8 9 FIG. No. 18   1  2 2  2  2  3  4  5  6 Bending angle α(°) 0 18 13 65 20 33 48 35 30 55Inclination angle β(°) 0 — 25 65 55 50 45 — — 35 Inclination angle γ(°)0 — — — — — — — — 38 Length δ(mm) 10  15 10 10  6 12  6 13  8  6 Lengthε(mm) 0 — 10 10 15  4 15 — — 15 Running distance (index) 100  115  103 102  120  127  125  130  123  115  Cracking rate (index) 100  103  98 9872 77 95 100  100  80

[0077] TABLE 2 Conventional Examples Items Example 10 11 12 13 14 15 1617 FIG. No. 18   7  8  9  9  9 10 11 12 Inclination angle α(°) 0 21 3813 65 23 35 30 50 Inclination angle β(°) 0 — 52 18 72 50 35 — 35Inclination angle γ(°) 0 — — — — — — — 38 Length δ(mm) 0 13 10 10 10 1515 18 15 Length ε(mm) 0 — 30 10 10 20 20 — 20 Running distance (index)100  120  127  103  102  124  130  125  120  Cracking rate (index) 100 103  76 98 98 72 95 98 85

[0078] TABLE 3 Conventional Examples Items Example 18 19 20 21 22 23FIG. No.  18 13 13 13 13 14 15 Inclination angle θ(°)  0 55 50 20 67 4045 Length δ(mm)  0 30 15 5 20 10 15 Running distance (index) 100 100 100  100  100  100  100  Cracking rate (index) 100 70 75 90 87 80 75

[0079] With respect to each tire of Examples 1˜23 and conventionalexamples as a test tire, a test for bead portion durability and a testfor crack resistance are carried out under the following conditionsafter the tire is mounted the tire onto an acceptable rim of 7.50×22.5among the approved rims defined according to JATMA standard (JATMA YEARBOOK, 1998) and a maximum air pressure of 8.5 kgf/cm² corresponding to amaximum loading capacity (SINGLE: 2720 kg, DUAL: 2500 kg) definedaccording to JATMA standard is applied to the tire-rim assembly.

[0080] In the durability test, the tire is run on a drum of 1.7 m indiameter at a speed of 60 km/h under a heavy load of 5000 kgf untiltroubles, mainly separation failure are caused in the bead portion 1.The running distance till the occurrence of the trouble is representedby an index on the basis that the conventional example is 100. Thelarger the index value, the better the property. The index value of therunning distance of each tire is shown in a lower column of Tables 1, 2,and 3.

[0081] The test for the crack resistance is a durability test in along-period test inclusive of recapping according to a test methodcalled as a long run test, in which the tire is run on the same drum asmentioned above at a speed of 60 km/h under a load of 4080 kgf over100,000 km and thereafter the tire is taken out therefrom and cut tomeasure a crack length in ends 5 e, 15 e of the organic fiber cordlayers 5, 15. A crack rate is calculated by dividing the crack length bythe running distance of 100,000 km and represented by an index on thebasis that the crack rate of the conventional example is 100. Thesmaller the index value, the better the property. The crack rate indexof each tire is shown in a lowest column of Tables 1, 2 and 3.

[0082] In general, as seen from the results of Tables 1 and 2, all ofthe example tires generally develop an excellent bead portion durabilityas to the reinforcement and strengthening of the bead portion becausethe running distance in all example tires exceeds the running distanceof the conventional example under a heaviest load, while as seen fromthe results of Table 3, all of the example tires show a bead portiondurability equal to that of the tire of the conventional example underuse condition of a heavy load and develop an excellent crack resistanceunder a long-period use condition inclusive of recapping, and hence thebead portion durability in the long-period use is improved based on suchan improvement of the crack resistance.

[0083] As the results of Tables 1 and 2 are examined in detail, eachtire of Examples 1˜7 not using the wire chafer 6 effective as a beadportion reinforcing layer show a durability exceeding the runningdistance of the conventional tire, and also the each tire of Examples1˜7 (former) is run over a distance equal to those of the tires ofExamples 8˜10, 12˜17 (latter) using the same two nylon chafers 5 andsingle wire chafer 6 as in the conventional example. The former cansimultaneously attain both weight reduction and improvement of beadportion durability, while the latter can attain the remarkableimprovement of the bead portion durability under the same weight andstructure.

[0084] As seen from the above test results, when the organic fiber cordlayer 5 has a first bent portion 5H₁ spread apart to the turnup portion4 t or the bead portion reinforcing layer 6 therealong toward theoutside of the tire and the first bent portion 5H₁ has a proper range ofa bending angle α, the organic fiber cord layer 5 develops an effectiverigidity as expected and sufficiently serves to mitigate stress in theend 4 te of the turnup portion 4 t or the end 6 e of the wire chafer 6.

[0085] Then, when the organic fiber cord layer 5 has a first bentportion 5H₁ bending toward the inside of the tire to the turnup portion4 t or the bead portion reinforcing layer 6 therealong and the firstbent portion 5H₁ has a proper range of a bending angle θ, the crackresistance in the end 5 e of the organic fiber cord layer 5 is improvedand hence the durability of the organic fiber cord layer 5 itself islargely improved.

INDUSTRIAL APPLICABILITY

[0086] According to the invention, the rigidity in a portion of theorganic fiber cord layer covering either one of an end of the turnupportion of the carcass and an end of the wire chafer extending outwardover the turnup end in the radial direction of the tire as a beadportion reinforcing layer can considerably be increased, whereby it ispossible to effectively mitigate stress applied to the ends during therotation of the tire under loading with the portion of the organic fibercord layer having the high rigidity and also it is possible toadvantageously improve the crack resistance in the end of the organicfiber cord layer. As a result, there can be provided a heavy dutypneumatic radial tire capable of considerably improving the bead portiondurability as compared with that of the conventional tire.

1. A heavy duty pneumatic radial tire comprising a carcass of at leastone rubberized cord ply of radial arrangement toroidally extendingbetween a pair of bead core embedded in bead portions and wound aroundthe bead core from inside of the tire toward outside to form a turnupportion, and at least one rubberized organic fiber cord layer extendingoutside the turnup portion over an end of the turnup portion outward ina radial direction of the tire, in which the organic fiber cord layer isarranged so as to extend from a position near to an outside of the beadcore over the end of the turnup portion toward the outside of the tireand spread apart to the turnup portion.
 2. A tire according to claim 1 ,wherein the organic fiber cord layer has a first bent portion acutelybending toward the outside of the tire with respect to a windingdirection of the turnup portion extending outward from the position nearto the outside of the bead core in the radial direction, and a bendingangle (α) of the first bent portion with respect to the windingdirection of the turnup portion at a radial section of the tire iswithin a range of 15˜60°.
 3. A tire according to claim 1 or 2 , whereina bead portion reinforcing layer made of a rubberized steel cord layeris disposed between the turnup portion of the carcass and the organicfiber cord layer and an outer end of the reinforcing layer in the radialdirection of the tire locates inward from the end of the turnup portionin the radial direction of the tire.
 4. A tire according to claim 2 or 3, wherein an end of the first bent portion of the organic fiber cordlayer is an outermost end in the radial direction of the tire.
 5. A tireaccording to claim 2 or 3 , wherein the organic fiber cord layer has thefirst bent portion and a second bent portion again bending from an endof the first bent portion toward an inside of the tire, and aninclination angle (β) of the second bent portion inclined with respectto the winding direction of the turnup portion is within a range of15˜60° at the radial section of the tire.
 6. A tire according to claim 5, wherein the organic fiber cord layer has the first bent portion, thesecond bent portion and a third bent portion extending outward from anend of the second bent portion at an approximately equal distance to anouter surface of the tire in the radial direction of the tire.
 7. A tireaccording to claim 2 or 3 , wherein the organic fiber cord layer has thefirst bent portion and the third bent portion extending outward from theend of the first bent portion at an approximately equal distance to anouter surface of the tire in the radial direction of the tire.
 8. A tireaccording to claim 7 , wherein the organic fiber cord layer has thefirst bent portion, the third bent portion and a fourth bent portionextending from the third bent portion toward the inside of the tire andacutely inclining with respect to the winding direction of the turnupportion.
 9. A tire according to claim 8 , wherein an inclination angle(γ) of the fourth bent portion with respect to the winding direction ofthe turnup portion is within a range of 15˜60° at the section of thetire.
 10. A heavy duty pneumatic radial tire comprising a carcass of atleast one rubberized cord ply of radial arrangement toroidally extendingbetween a pair of bead core embedded in bead portions and wound aroundthe bead core from inside of the tire toward outside to form a turnupportion, at least one bead portion reinforcing layer made of arubberized steel cord layer extending outside the turnup portion over anend of the turnup portion, and at least one rubberized organic fibercord layer extending outside the turnup portion over an end of theturnup portion outward in a radial direction of the tire, in which theorganic fiber cord layer is arranged so as to extend from a positionnear to an outside of the bead core over the end of the turnup portionof the bead portion reinforcing layer toward the outside of the tire andspread apart to the turnup portion.
 11. A tire according to claim 10 ,wherein the organic fiber cord layer has a first bent portion acutelybending toward the outside of the tire with respect to the bead portionreinforcing layer extending outward from the position near to theoutside of the bead core in the radial direction and the extendingdirection thereof, and a bending angle (α) of the first bent portionwith respect to the winding direction of the turnup portion at a radialsection of the tire is within a range of 15˜60°.
 12. A tire according toclaim 11 , wherein an end of the first bent portion of the organic fibercord layer is an outermost end in the radial direction of the tire. 13.A tire according to claim 11 , wherein the organic fiber cord layer hasthe first bent portion and a second bent portion again bending from anend of the first bent portion toward an inside of the tire, and aninclination angle (β) of the second bent portion inclined with respectto the winding direction of the turnup portion is within a range of15˜60° at the radial section of the tire.
 14. A tire according to claim13 , wherein the organic fiber cord layer has the first bent portion,the second bent portion and a third bent portion extending outward froman end of the second bent portion at an approximately equal distance toan outer surface of the tire in the radial direction of the tire.
 15. Atire according to claim 11 , wherein the organic fiber cord layer hasthe first bent portion and the third bent portion extending outward fromthe end of the first bent portion at an approximately equal distance toan outer surface of the tire in the radial direction of the tire.
 16. Atire according to claim 15 , wherein the organic fiber cord layer hasthe first bent portion, the third bent portion and a fourth bent portionextending from the third bent portion toward the inside of the tire andacutely inclining with respect to the winding direction of the turnupportion.
 17. A tire according to claim 16 , wherein an inclination angle(γ) of the fourth bent portion with respect to the winding direction ofthe turnup portion is within a range of 15˜60° at the section of thetire.
 18. A heavy duty pneumatic radial tire comprising a carcass of atleast one rubberized cord ply of radial arrangement toroidally extendingbetween a pair of bead core embedded in bead portions and wound aroundthe bead core from inside of the tire toward outside to form a turnupportion, and at least one rubberized organic fiber cord layer extendingoutside the turnup portion over an end of the turnup portion outward ina radial direction of the tire, in which at least a cord layer portionof the organic fiber cord layer located at the side of the turnupportion has a first bent portion bending such that its outer end isinclined toward an inside of the tire in a radial direction thereof. 19.A tire according to claim 18 , wherein a bending angle (θ) of the firstbent portion with respect to the winding direction of the turnup portionis within a range of 15˜70° at the section of the tire.
 20. A tireaccording to claim 18 or 19 , wherein a bead portion reinforcing layermade of a rubberized steel cord layer is disposed between the turnupportion of the carcass and the organic fiber cord layer, and an outerend of the reinforcing layer in the radial direction of the tire locatesinward from an end of the turnup portion in the radial direction of thetire.
 21. A tire according to claim 18 or 19 , wherein a bead portionreinforcing layer made of a rubberized steel cord layer is disposedbetween the turnup portion of the carcass and the organic fiber cordlayer, and an outer end of the reinforcing layer in the radial directionof the tire locates between an end of the turnup portion and an outerend of at least cord layer portion of the organic fiber cord layerlocated at the side of the turnup portion of the carcass, and the firstbent portion locates outward from the outer end of the bead portionreinforcing layer in the radial direction of the tire.
 22. A tireaccording to claim 18 or 19 , wherein the end of the first bent portionof the organic fiber cord layer is an outermost end in the radialdirection of the tire.
 23. A tire according to any one of claims 2˜9,11˜16, 18, 19, 21 and 22, wherein each length of the first bent portion,second bent portion and third bent portion of the organic fiber cordlayer is within a range of 4˜50 mm.
 24. A tire according to any one ofclaims 1, 10 and 18, wherein the organic fiber cord layer is suitable tobe a nylon cord layer.